A/N: I realize I already have a couple of zombie apocalypse AUs published, but after seeing this prompt, the idea was such a fun one to explore and the fill just happened. Apologies in advance!


Prompt from 'castleficpromoter's list of Halloween Bash ideas:

4x22, Undead Again, AU: The killer really was a zombie.


"So do we have cause of death?" Beckett asks as the body of Kyle Jennings is wheeled into the morgue, ignoring Castle and Perlmutter's sarcastic back and forth jabs at one another, studying the decomposed victim on the slab.

It's all fake, prosthetics and stage makeup, but it unsettles her how real the decaying skin of the man's face looks, the sharp prominence of bone beneath, the warmth his body emits despite being dead for hours now.

She's torn away from her examination when Castle stops Perlmutter from proceeding with the autopsy, a question bubbling on his lips.

"Before this man died, he was behaving exactly like he was a zombie. So, is there any medical way to determine if he actually was… one?"

Beckett rolls her eyes, prepares for Perlmutter's wrath.

"Why is he in my morgue?" the medical examiner demands in exasperation. "There are no zombies, Castle. This is a man. He was a live man, but now he's a dead man. End of story, now-"

Perlmutter is cut off by the sudden jerk of said dead man beneath him, the ripple of awareness as his eyes snap open to reveal a very much alive body on the slab, but despite his revival, Kyle Jennings hardly looks human. His eyes are dark, bloodshot and unseeing, lifeless, but when they land on Perlmutter hunched above him, the ink black pupils dilate.

"Get back," Beckett warns, grabbing Castle by the arm and tugging him away from the body, the hands twitching at its sides. "Perlmutter-"

"Hold on, Detective, let me check his-"

"Beckett," Castle murmurs, drawing her back towards the door with him, his arm extending out in front of her as if he could protect her from the man growling on the table, but she refuses to give him the chance. "I think you should call for backup."

Kate fishes her phone from her pocket, but Kyle is already writhing on the metal table, arms flailing, hands grabbing for Perlmutter, lunging for the M.E with an open mouth.

She replaces the phone with her gun.

"Perlmutter, get back!"

One of the assistants in training rushes in to help, grabbing Kyle by the shoulder and quickly earning the dead man's attention, gaining the sink of his teeth into the young trainee's arm, eliciting screams that echo through the room as Kyle rips the flesh from bone.

Beckett fires a round into Kyle's back, but even as her bullets penetrate the man's upper body, he doesn't stop.

"Charlie," Castle utters. "That - that guy we interviewed yesterday, the one who was bitten, he was right," he gets out, hooking his fingers at her elbow and jerking her back as Kyle tackles Perlmutter to the ground, but she can't get a shot like this with the man on top of him, biting into his throat and muffling the M.E's screams. "He's actually a zombie."

She fires again, empties her clip into Kyle, but he won't stop, doesn't stop until her last bullet pierces his skull.

"No," she whispers, because it's not possible. Zombies? That entire myth was just fodder for TV shows and horror movies. It isn't real, can't be real-

"We have to go, Kate," Castle urges, yanking her back through the swinging door until she finally turns, doesn't withdraw the hand he's claimed in his own, and runs with him towards the exit.

"Castle," she gasps after him, sprinting up the stairs to street level by his side, her eyes scanning the sidewalks filled with people. Normal people, nothing out of the ordinary, making everything she just witnessed down in the morgue feel as if it was nothing more than a horrific hallucination. "Wait, we can't just-"

"Look, I know you don't buy into stuff like this," he throws back over his shoulder, hustling back towards her cruiser. "But I do and even if it's all some mistake and the world is not about to go into zombie apocalypse mode in a matter of hours, just humor me."

But she can't just run away. There were two dead people inside the building at their backs, an unfortunate bystander passed out from shock and blood loss on the morgue's not so pristine floors, and she's a cop, her job is to protect and serve. Not retreat and hide.

"Rick-"

He stops abruptly at the driver's side door, has her bumping into his chest and bracing herself with a hand to his sternum.

"You may not care, but I'm not losing you again," he states under his breath, his eyes a thunderous shade of blue burning bright in the darkness of night all around them. "Definitely not like this. So just - we need to find someplace safe."

She shouldn't indulge him, feed into this delusion of a zombie apocalypse, but she's too hung up on how he doesn't want to lose her even after he'd said this was his last case, even after he'd wanted to leave her.

Kate releases his hand to open the door, nudging him to the passenger side before she slides into the driver's seat and keys the ignition.


She speeds on their way back to the precinct while Castle calls Alexis, his mother.

"No, Pumpkin, listen," he murmurs, his voice soothing, not panicked like the look on his face, like the quivering of his fingers on his knee. "Remember last year when I told you and Gram to go to the Hamptons? Yeah, when the bomb threat happened," he sighs, scrubbing at his eyes. "It's not that, just - trust me? I'll meet you there this time, I promise."

Beckett chews on her bottom lip, piercing the flesh and tasting the faintest hint of blood on her tongue. His fear was beginning to spread to her, the preposterous idea suddenly starting to feel all too real, but she forces herself to block it out, refuses to buy into it. She would play along for now, for Castle's sake, but after his theory was proven wrong, she'd return to the morgue, give her statement - if she can manage to make sense of what she saw - and make up for her cowardly exit.

"I love you too, see you tomorrow, Pumpkin. And just remember, no stopping." Castle withdraws the phone from his ear and cuts his gaze to her. "We'll do our best to meet them in the Hamptons. After that, I have a bunker further upstate."

"A bunker?" she repeats incredulously, but he isn't joking; she actually can't recall the last time she witnessed Castle appear so deadly serious.

"We'll be safe there, it's fully stocked, but we should probably stop at your place first, get what you need-"

"But the case," she protests weakly and it's his turn to shoot her an incredulous look.

"What case? The killer is an actual zombie, who probably turned Perlmutter and that other kid into zombies, and we know this guy wasn't even Patient Zero-"

"There's no way this is the zombie apocalypse," she argues, her fingers clenching around the steering wheel. "There's not – they would be everywhere, it'd be mass chaos."

"Not right away," he points out. "It'll build slowly at first. And we already went over this, even if I am wrong – which I am nearly positive that I am not – just come with me until it's proven. If it's nothing, turns out to be one big fluke, you can come right back to work and blame this all on me and my outlandish theory, you already know Gates will buy that without blinking."

Kate purses her lips and pulls up in front of the precinct. "Fine. Let me just grab my stuff from my desk and then we'll stop by my place and go."

"All I ask," he nods, exiting the car with her, sticking close to her side as they cross the street and enter the Twelfth.

"What the hell am I supposed to tell Gates?" she mumbles in the elevator, her palms sweating with nerves. She's essentially about to play hooky during an open investigation and it has her stomach in knots, but parting ways with Castle now would be worse, would have a full-fledged war waging on her insides.

"Don't tell her anything," Castle shrugs, checking his watch. "She usually takes a break around this time anyway, so we'll likely make it in and out without her even noticing."

The elevator opens onto the homicide floor and Castle jogs straight for Ryan and Esposito's desk while Beckett strides to hers, unlocks her drawer with fingers that tremble and hauls her bag over her shoulder, snags her extra piece from the bottom drawer.

"Yo, what's this about you running away with Castle?" Esposito questions under his breath, but when she glances up at him, he straightens, assesses her with a rare hint of concern. "What the hell happened? You look like you saw a ghost."

"Not a ghost, a zombie," Castle whispers over Espo's shoulder and Kate rolls her eyes, but her hand still shakes. "I'm telling you, Esposito, you guys need to come with us. Or at least meet us out there. I gave Ryan the directions to both my Hamptons place and the bunker so-"

"Bunker? What the hell?" Esposito hisses, but Castle is waving him off. "Beckett, you seriously buying this crap?"

"I - I don't know," she confesses, scraping her fingers through her hair. "Perlmutter is dead. The guy dressed as a zombie, Kyle, he - he came back to life-"

Ryan is joining their huddled trio, staring back at her with eyes that look as if they're about to bulge from their sockets. "What?"

"Perlmutter was about to cut him open and it was like he jerked away, went straight for him," Castle explains in a low murmur. "Kate emptied her clip into his back, his chest, and it didn't make a difference. Not until she shot him in the head."

She nods when both boys turn to her for confirmation and Ryan pivots on his heel, heading back for his desk with his phone already in his hand.

"I wouldn't be against you, Ryan, Lanie, and Jenny following us out of the city as soon as you can," she adds, swallowing against the disbelief in Esposito's eyes. "Better safe than sorry, I guess."

Castle musters a proud grin that falls flat at Esposito's side and then he's reaching for her hand again. "Feel free to raid the armory on your way out."

"Castle," she huffs, stumbling after him, and she thinks that's what convinces Esposito to begin taking this seriously.

"Hey, you gave Ryan the addresses?" he asks before they're out of earshot and Castle nods. "We'll wait in the Hamptons until tomorrow, then we're moving forward. Phone lines will likely be down by tonight, early morning depending on how all of this goes down, so call as soon as possible if you can."

And the fact that Esposito accepts the information with a solemn nod, shares a look with Ryan from a few feet away, has her heart pounding a little harder.

This can't be happening, can it?

"See you soon, stay safe and stay off the streets," Castle says under his breath, nodding to Ryan who is on his cellphone, talking too fast to whom she assumes is his wife.

She walks wordlessly with him back towards the elevator, her bag too heavy on her shoulder, and Castle squeezes her hand.

"Don't worry, Beckett," he tells her as the doors slide shut, his thumb stroking her knuckle just once, and she lifts her eyes to find his watching her. It's been so long since he's looked at her without resentment that she still doesn't understand. "We're going to be okay."

"Zombie apocalypse or not?" she rasps, clearing her throat with an ashamed quirk of her lips, but Castle is staring back at her with a flicker of surprise in his eyes before resolution claims his gaze, squares his jaw.

"No matter what," he says, twining their fingers seconds before the doors part. "I'm with you."


It doesn't take long for riots to break out into the streets, for the undead to blend with the living in the crowds, for assemblies to turn into massacres.

"We gotta go," Castle calls to her from her living room and Kate yanks her duffel bag from the bed, rushes back to the main room and follows his gaze out the window. "Shit, we really need to go. I didn't think it'd spread this fast."

Her stomach drops out at the sight below her windows, the view into the street, the chaos she'd spoken of earlier but had hardly expected to actually see.

"Castle, if this is - it's real, it's actually happening, but it's my job to-"

"With all due respect, screw the job right now, Kate," he mutters, leading her away from the window, scanning his eyes over the interior of her apartment as if this is the last time he'll be seeing it, and it opens a chasm of terror in her gut. She may never see her apartment again, may never see her old life again, and she's not – god, she's not ready. But who is? "You stay and you get ripped apart or trapped."

"What if it's controllable?" she reasons, but she's following him across the room with her bag slung over her shoulder. "What if they manage to quarantine the infected, stop the outbreak before it spreads?"

"Does it look controllable?" he questions with a tilt of his head towards the window and she doesn't have to look back to hear the screaming, the panic happening right outside, the prelude to a full-blown disaster. "You have everything you need?" he asks, already starting for her door, swinging it open and striding out into the hall while she locks up.

"Yeah, I hope," she mumbles, striding ahead to lead him down the stairs, out the side door of the building that exits into an alley, closer to where her Crown Vic is parked.

They almost make it without issue.

She has her first real encounter with the undead seconds before they can reach the car. A tall male in a torn business suit is blocking their way, shuffling towards them with an exaggerated limp, releasing snarling noises that intensify with every staggering step.

"NYPD!" she shouts out of instinct, raising her weapon, but the man keeps coming, growling at her, baring bloodstained teeth. "Stop!"

"Kate," Castle urges from her side, his hand on her hip. "You have to shoot it. It's not going to stop, it's not going to-"

"Stop!" she tries again, because it worked with that fake horde of walkers hours earlier, when it was all just an innocent nighttime hobby, when the threat was nothing to actually worry about. "This isn't a game!"

The walker is inches away from her, inhuman eyes staring back at her, decrepit fingers reaching out, doing exactly as Castle said – not stopping.

Until Castle is the one who makes him.

His arm come over her shoulder, her extra piece in his hand and aimed at the zombie's head, firing and sending the corpse crumpling at her feet.

"Castle," she breathes, but he has an arm around her waist, dragging her around the body of the dead, and ushering her into the passenger seat.

He takes her usual spot on the driver's side, revs the engine, and peels into the street.

"You… you killed someone," Beckett whispers, but she knows that thing wasn't a person, that what Castle had done wasn't murder.

"Something," he corrects quietly, sparing her a look as he maneuvers through the crowds and residual traffic with impressive skill, and Kate stretches her arm across the space between them, dusts her fingers at his cheek.

He startles a little but keeps his hands on the wheel, his eyes on the road, while she wipes away the blood spatter on his skin.

She believes him now.


"Are you okay?"

Kate blinks, fighting past the shock and exhaustion glazing over her eyes, and glances up to find Castle watching her. It's nearly four in the morning and they're free of New York City, of their homes and friends and lives, of the undead that she's sure have swarmed Manhattan and the surrounding boroughs by now.

"Yeah," she croaks, taking a sip of the water bottle he'd handed her an hour ago. "I'm just - I'm sorry, making you shoot when I should have."

"Don't be sorry," he murmurs, reaching for one of her bent knees that's propped against the packed duffel situated between them in the front seat, squeezing her patella with his warm palm. "I'd do it again."

She swallows, hopes that no matter the circumstances, it doesn't come to that.

"I'm not used to being… out of my element, I guess," she murmurs, still amazed at how in his element that Castle seems to be in this terrifying epidemic.

They'd had the radio on for the first hour, listened to the reports of the death toll rising, both figuratively and literally, warnings of an infection spread by the sink of teeth into skin and the existence of a zombie apocalypse finally coming true. But the breaking news announcements had quickly died out and turned to static, the stations all going dark and silent, the cell service following. He'd exchanged a final text with Alexis, asking if she was safe in the Hamptons not long after they had hit the road but never receiving an actual answer, and Kate had spent a handful of seconds on the line with Esposito, received confirmation that he and Lanie were meeting with Ryan and Jenny to evacuate, but that had been hours ago and she hadn't heard anything since. And she knows she won't.

The world is steadily going dark.

"You're definitely not the only one, Kate," he promises, and it strikes her then, that it's the first time he's said her first name in so long, the first time he's spoken it with warmth, touched her with such tenderness. "There's no way to be ready for this and you're a cop. You're trained to talk people down, not shoot on sight."

"And you are?" she counters, swaying her knees into the drape of his palm, watching him navigate easily on the practically empty highway. They must have really beat the majority in evacuating and something about that makes her sick to her stomach.

"I read a lot of apocalyptic planning books before this and do you know how many episode of The Walking Dead I've seen? Even went to zombie survival training camp a few summers ago with Alexis."

The corners of her mouth quirk and Kate covers his hand on her knee.

"Thank you."

He squeezes her hand once before letting go, returning his grasp to the wheel. "Partners."

"Yeah?"

His brow furrows, but she doesn't take back the uncertainty, because if this is their extinction event, how the world finally ends, she refuses to concede to damnation without knowing the truth and sharing her own.

"You doubt that?" he murmurs, the line of his jaw sharpening, his hand loosening atop her kneecap, so she laces her fingers through the empty spaces of his and squeezes.

"These last few weeks I have," she confesses, casting her gaze to the sky above, indigo with the sprinkle of stardust. Peaceful if not for the devastation she knew they had just left behind. "You… stopped. Stopped being my partner for a while."

His foot eases from the accelerator, shifts to the brake, and slows the car to a stop along the side of the road.

"What are you doing? We can't stop," she murmurs, sitting up a little straighter and glancing around, but they're alone, not a car or human in sight.

"No, we can't, but what I have to say will only take a moment and it can't wait any longer," Castle sighs, his head turning to face her in the darkness, the light of the moon bathing his cheek in the pale glow, and her heart lodges itself in her throat in a different form of fear. "I love you, Kate. And I - I wanted to stop, tried to make myself stop loving you."

She recoils, those words slicing through her, more unbearable than facing down the undead. Was it even worth it if he isn't fighting with her, for her anymore?

"Beckett." Back to Beckett, she curls her fingers at her chest, the throbbing heat of the scar between her breasts. "Kate-" Better, but still no good, no help to her cracking heart. He doesn't want her anymore, not like she wants him, and she doesn't know how to accept that. "It's okay, it's - it'll still be okay. I'm still here, no matter what, and I realize you don't feel the same, but that doesn't mean I-"

"What?" she rasps, grief and confusion scraping her throat raw as her heart slides back into her chest, snagging on the bones of her ribs.

"I just wanted you to know, but I don't want you to think we aren't still partners. I just needed some time to accept it, still need time, honestly, but I don't think that luxury exists anymore," he chuckles, hollow and raw and heartbroken. "I'm sorry if I hurt you these last few weeks, I wasn't trying to punish you, I just didn't know how to… I'll learn to love you solely as a friend, I promise-"

"No," she protests, shoving her bag to the backseat and inching closer to him, shaking her head even as her palms find his cheeks, cradle his face in unsteady hands. "Fuck, Castle, we have the worst timing."

His brow quirks and so do her lips, because he really doesn't know, doesn't have any idea.

"I waited too long," she rasps, clamping down on her bottom lip with her teeth to stop it from quivering. They had just survived an escape from a corpse-ridden New York City and she refuses to cry now. "I should have told sooner, so much sooner."

Castle catches her wrist in one of his hands, his fingers banding around the bone, sealing over the rabbiting of her pulse.

"Told me what, Kate?"

She swallows and presses in closer, drops her forehead to rest against his and brushes her nose to his cheek, feels the hitch in his chest and the stutter of his breath fan across her lips.

"That I love you back," she answers, swiping her thumbs along his skin. "That I have for a while now, but I thought – I always thought we'd have more time." She nearly chokes on the words, the weight of them, how quickly their time could come to an end now and how she waited until their final moments to finally tell him, to witness the bloom of wonder through his eyes, the tenderness that fills the striking blue of his gaze, the love she hasn't seen in far too long. "But don't accept that I don't feel the same because you're wrong, don't - I don't want you to just be my friend, don't stop loving me-"

Castle tilts forward to kiss her, soft and gentle, his lips tending to the surface of hers before his tongue caresses the seam of her mouth, slips inside and has her mind cleansed of the horrors they've experienced within the last twelve hours, replacing it with the beautiful sensation of his mouth on hers.

"We'll have more time," he promises, lips still brushing hers as he speaks, making it hard to concentrate, but her eyes flutter open, lashes twining with his. "Because no way am I dying now."

She smiles for the first time since the outbreak, for the first time in the last few weeks, and seals one last kiss to his mouth before drifting back into her seat.

"Good, didn't plan on letting you die anytime soon," she mumbles, watching him shift the car back into gear, his foot returning to the gas pedal.

"And it's not even for the sake of avoiding paperwork anymore," he muses, the corner of his mouth curling into a smirk. "You must really love me, Beckett."

She rolls her eyes, but there are butterflies in her stomach, fluttering along her insides and tickling her exposed heart, spreading joy through her system. Because he still loves her, even at the end of the world.